A former state prosecutor who published a book detailing rights abuses in the ruling Chinese Communist Party's own disciplinary system was hounded by police and had his computer hacked, he told a launch party for the book in Hong Kong on Monday.

Shen Liangqing's book Double Discipline: an Investigative Report by a Former Prosecutor shows Party investigators "doing anything they like," he said in a speech posted online on Monday.

"The law shouldn't be the tool of a one-party dictatorship," he added.

Shen's book details the inner workings of the Party's "shuanggui" disciplinary process, which was recently undergone by former Chongqing Party boss Bo Xilai, who was expelled from the Party last month for graft and for his involvement in the murder of British businessman Neil Heywood, for which his wife Gu Kailai was handed a suspended death sentence in August.

Shen was prevented from traveling to Hong Kong for the book launch by police, who held him under unofficial detention at a tourist resort.

He said they had also prevented him from getting hold of a copy of his own book.

"The police had been coming to my home every 2-3 days since February," he said. "They said that, while they couldn't change my views, they had turned a blind eye to my many criticisms of the government over a number of years."

Outside the law

U.S.-based political commentator Liu Nianchun said the "shuanggui" internal Party disciplinary process operates outside the law.

"There are laws, and they are well-conceived, but they aren't implemented," he said, adding that internal Party documents still carry far greater weight in China than do the laws on the statute books.

Meanwhile, Beijing-based lawyer Wang Yajun said the "shuanggui" system is a throwback to the Mao era of kangaroo courts and political "struggle sessions" which took the decisions of the Party as a form of law.

"For several decades we only had a handful of laws," Wang said. "There was a marriage law, a land law and so on, but no criminal law or regulations on the right of appeal."

Wang said the system for interrogating Party members is mirrored by a similar system for internal investigations into civil servants who aren't Party members.

"Whichever [system] it is, in actual practice they're both about limiting a person's freedom," he said.

Coercive measures

Fellow lawyer Tang Jitian agreed: "Shuanggui is basically a form of coercive measure outside the law."

Shen, a former official at the state prosecution service in the eastern Chinese province of Anhui, told guests at the book launch that he was repeatedly contacted by police wishing to "take him out to eat," and had declined a number of times for "health reasons."

He said during a video call from his home that he was relieved that the Anhui authorities had been unable to prevent the publication of the book in Hong Kong, however.

"I could see via Skype that the launch was under way, and that they all had copies of the book," Shen said.

"It was very hard to get this book ... out; I had every kind of [official] interference."

Party Congress

Last Thursday, the Party began its 18th national congress to decide who will get the top jobs during a once-in-a-decade leadership transition amid China's worst political scandal in decades.

The Central Committee last month expelled fallen Chinese political star Bo Xilai from its ranks following accusations of corruption and sexual misconduct, removing his parliamentary privilege and paving the way for a criminal trial.

The announcement came after Bo was held for months at an unknown location during a "shuanggui" disciplinary procedure.

Bo was also judged to bear "major responsibility" in the murder of British businessman Neil Heywood, for which his wife Gu Kailai was handed a suspended death sentence by a court in Anhui on Aug. 20.

His former police chief and right-hand man Wang Lijun was jailed for 15 years in September for "bending the law for selfish ends," "abuse of power," and "defection," after his Feb. 6 visit to the U.S. consulate in Chengdu brought the scandal to public attention.

Reported by Yang Jiadai for RFA's Mandarin service and by Wen Yuqing for the Cantonese service. Translated and written in English by Luisetta Mudie.